In general, various processings, such as film formation, etching, oxidation, diffusion and the like, are performed on a semiconductor wafer to manufacture a semiconductor integrated circuit. Along with a recent trend of miniaturation and high integration of a semiconductor integrated circuit, there has been a strong demand for improvements of throughput and yield. For meeting such a demand, a so-called clusterized processing system has been disclosed in Japanese Patent Laid-open Application No. 2000-208589, wherein plural processing apparatus for performing an identical processing or different processings are coupled to each other through a common transfer chamber, and thus, different processings may be continuously performed on a wafer while the wafer is not exposed to the air.
In such a processing system, the wafer is handled as follows. First, the wafer is transferred by a first transfer mechanism from a cassette container installed in an inlet port, which is provided at a front end of the processing system, to be loaded into an inlet side transfer chamber of the processing system. After the wafer is position-aligned by using a position-aligning mechanism, it is loaded into a load-lock chamber that can be vacuum-exhausted. Subsequently, the wafer is loaded by using a second transfer mechanism into a common transfer chamber under a vacuum atmosphere, to which plural vacuum processing apparatus are connected. The wafer is sequentially introduced into the respective vacuum processing apparatus by using the common transfer chamber as a center, and thus, being continuously processed. A processed wafer is transferred along a same route as in the loading, but in a reversed order, to thereby be accommodated in the original cassette container. Such a processing system has therein a single or plural transfer mechanism(s); and an exchange or a transfer of the wafer is performed in an automated manner by using the transfer mechanism(s).
Such a transfer mechanism has one or two pick(s) capable of freely contracting and extending, revolving and elevating. The wafer is directly supported by the pick to be moved in the horizontal direction, so that it is transferred to a predetermined position. While the transfer mechanism is operated, the pick and the wafer kept therein should be prevented from being interfered by or from colliding with other members. Moreover, the pick needs to properly unload the wafer placed on a specified place to transfer same to a destination, and to perform an exchange of the wafer at the destination with high accuracy, e.g., positional accuracy within ±0.20 mm.
For the same reason, in case when an assembling or a large device remodeling is performed, a so-called ‘teaching operation’ has been performed, wherein an important place, e.g., a place where an exchange of the wafer W is performed at a moving route of the pick of the transfer mechanism, is stored as a set of delivery position coordinates in a controller formed of a computer or the like, which controls an operation of the transfer mechanism. The teaching is performed on each pick for all access points thereof (e.g., access points of the pick to the cassette container, the mounting table of the load-lock chamber, a position-aligning device and a susceptor of each vacuum processing apparatus); and sets of delivery position coordinates defining these access points are stored in the controller. Further, a driving unit of a transfer device has therein an incorder for specifying a pick position. The driving unit has a pulse motor as a driving source; and the number of pulses applied to the pulse motor is controlled based on a detection result of the incorder to control the pick position precisely.
A teaching method of a transfer system in a clusterized processing system has been disclosed in Japanese Patent Laid-open Application No. 2000-127069. When performing the teaching, there is employed a dummy substrate made of a transparent plate having substantially identical diameter and thickness to a semiconductor wafer to be transferred. On the dummy substrate, an outline of the pick is marked at a position where the pick will support the dummy substrate. If the marking coincides with the outline of the pick, the dummy substrate is considered to be kept at a proper position on the pick.
The teaching is performed by following a sequence as explained below. First, a set of delivery position coordinates is temporarily determined in advance with ‘rough accuracy’ before the teaching is performed with high accuracy. The term used herein ‘rough accuracy’ refers to an accuracy, wherein the wafer is made sure not to collide with members, e.g., an inner wall of the chamber and the like, even while it is automatically transferred based on this temporarily determined set of delivery position coordinates; and it may contain an error, e.g., about ±2 mm, for a finally fixed set of delivery position coordinates. Subsequently, the dummy substrate is mounted at a very accurately determined proper position by being manually position-aligned at a delivery position on a mounting table in the load-lock chamber, on a susceptor of the vacuum processing chamber or the like. Further, the dummy substrate is unloaded by the pick to be transferred to an orienter as a positioning mechanism, which detects a positional displacement. The temporarily determined a set of delivery position coordinates is corrected based on the positional displacement detected, and the corrected set of delivery position coordinates is stored in the controller as a fixed set of delivery position coordinates. The aforementioned teaching operation is performed on each pick for all access points thereof.
In the teaching method as mentioned above, a position alignment should be performed carefully on all access places to each pick by an operator with the naked eye by using a manual. For the same reason, there are problems that the teaching needs to be performed for a long time, thereby burdening the operator.
Further, in case where the wafer unloaded from the cassette is transferred to the susceptor of the processing device, a position of the wafer to be mounted on the susceptor may be slightly shifted for each transfer route through which the wafer passes, since a manual position alignment is carried out for each pick on a place where the pick accesses.